This invention relates to a process and apparatus for subterranean monitoring and sensing subsurface parameters. More specifically, the invention relates to a cone penetrometer having a deployable sensor which is positionable away from the penetrometer surface. The extension of the sensor facilitates readings and data collection in a region outside the compression zone which forms upon deployment of a cone penetrometer.
Contamination of subsurface soil and its environmental impact has been the subject of considerable public attention and has caused much concern with respect to the storage and disposal of waste materials given the potential for contamination. It is common for contaminants or hazardous materials to lodge in the interstices or pore space of the soil or to become part of the soil solutions, which can be generally defined as the interstitial water in the soil together with solutes and dissolved gases. Early detection and monitoring of such hazardous materials in subsurface soil solutions is critical so that problems can be addressed before a hazardous material or condition spreads. The need exists, therefore, for methods and apparatuses for obtaining accurate and representative samples of liquid and/or gas from subsurface soil. Further, absent any concern for hazardous materials, it is important and useful to be able to obtain subsurface samples for various other scientific purposes.
A common technique for subsurface site characterization utilizes a cone penetrometer system equipped with various sensors. The penetrometer system consists of a truck equipped with a vertical hydraulic ram that is used to force a rod with an umbilical cord into the ground at varying depths. It is known within the art to provide a suction device mounted near the rod to permit sample vapors from the soil to be transported via a tube for analysis such as a gas chromatograph coupled to a mass spectrometer. As the rod is pushed or retrieved from the ground, a vertical profile of soil conditions may be obtained. Repeated vertical profiling at various locations results in a three-dimensional mapping of a potentially contaminated site.
A variety of devices are known within the prior art for the sampling of subsurface soil and conditions. For instance, it is known in the art to use devices such as lysimeters which a vacuum pull-through conduit to draw soil solutions samples into a receptacle and through the conduit to the surface of the ground. For instance, U.S. Pat. No. 4,759,227 to Timmons, which is incorporated herein by reference, teaches an apparatus and process disclosing a lysimeter which utilizes a rigid, porous, fluoroplastic filter section through which soil moisture surrounding the lysimeter may be collected and introduced into a chamber of the lysimeter.
U.S. Pat. No. 5,035,149 to Yierenga discloses a lysimeter-type sampler having a tube-like porous stainless steel receptacle which permits entry of a subsurface solution. A second tube forms a non-porous stainless steel conduit is joined to the end of the first two. A series of alternating vacuum and pressure changes provides a pressure gradient for conveying the collected sample to the surface.
U.S. Pat. No. 5,209,129 to Jaselskis et al. discloses a subsurface sampler in which an outer cylindrical casing defines a series of portholes. The portholes are normally sealed during the insertion operation. Following insertion, an inner sleeve of the casing is partially rotated so that the portholes are exposed to the subsurface conditions. A tab or wiper is attached to the inner sleeve to clear a small space of blocking soil immediately alongside the outer surface of the casing.
U.S. Pat. No. 5,165,274 to Thiercelin discloses a down hole penetrometer which the penetrometer defines a tooth and an associated actuator for extending the tooth radially outward from the body so as to penetrate the wall of the bore hole. The arrangement is used to determine pore pressure prior to undertaking commercial drilling or hydraulic fracturing techniques.
U.S. Pat. No. 5,889,217 to Rossabi et al. discloses a cone penetrometer which is hydraulically pushed into the ground while in situ measurements are continually collected. The cone penetrometer provides a filtering zone in which samples of liquid and gas from subsurface oil may be collected and transported to the ground surface without having to return the apparatus itself to the surface.
One disadvantage of the above collection methods and apparatuses involves the substantial pressures required to insert the measuring device into the subsurface of the soil. Insertion of a cone penetrometer or similar structure creates compression zones in which the soil adjacent the penetrometer is compacted and undergoes other possible changes as a result of the compression pressure which results from insertion. As a result, it is by no means certain that measurements taken from within the compression zone accurately reflect the subsurface characteristics of the surrounding, non-compressed regions. Accordingly, there remains room for variation and improvement within the art.
The present invention is directed to a method and apparatus for positioning a sensor at a variable distance from the surface of a deployed cone penetrometer. It is a principal object of the present invention to provide an apparatus and method for positioning a below ground sensor outside a compression zone created upon the insertion of a cone penetrometer.
It is a further object of the present invention to provide a cone penetrometer having a pivoting arm which forms a portion of the exterior surface of the penetrometer. Upon deployment, the pivoting arm extends beyond the soil compression zone and facilitates the placement of a sensor on the terminal end of the deployed arm.
It is yet a further object of the present invention to provide a penetrometer having a deployable arm which may be extended variable distances from the surface of the penetrometer, thereby facilitating subsurface measurements both within and beyond a soil compression zone.
In accordance with the objects of the invention, the present sensor apparatus may obtain in situ measurements from a subsurface environment, the sensor apparatus having a tubular shaft having an exterior cylindrical wall and defining an interior cavity, the exterior wall further defining an opening; an arm being pivotally mounted via an axle which is operatively disposed within the tubular shaft, the arm being movable relative to the shaft between a closed position covering the exterior wall opening and a deployed position where a free end of the arm extends away from the surface of the tubular shaft; a motor disposed within the tubular shaft and in operative engagement with the axle; a sensor carried by the free end of the arm and in further communication with an interior of the tubular shaft; wherein, when the motor engages the axle, the axle is rotated and thereby pivots the arm from the closed position covering the shaft opening to a deployed position with the free end of the arm and the associated sensor positioned away from the exterior wall of the shaft.
These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims.